1,721,044 research outputs found
Theory of light emission in sonoluminescence based upon transitions in confined atoms
No full textA theory of light emission in sonoluminescing hydrogen bubbles,
based upon transitions in confined atoms, is proposed. Despite the
simplicity of the assumptions this model accounts for a number of facts
related to sonoluminescence: a broadband spectrum in the correct
wavelength window is predicted as well
as the number of emitted photons. Taking the temperature at the moment
of collapse as a
parameter we argue that confined atomic transitions at 4000 K may account for
the observed light emission. This result favours a `cold' interpretation of
sonoluminescence in contrast to previous theories.
Many considerations are qualitatively extendible to rare gases
Effective wind actions on ideal and real structures
No full textGust buffeting of structures is analyzed by Double Modal Transformation, a method consisting in the
joint transformation into principal components of structural displacements (modal analysis) and of
wind loading (proper orthogonal decomposition). It commonly occurs that modal truncation applies to
both the series of structural and loading modes; besides, many loading modes are almost orthogonal
respect the dominant structural modes, so they do not contribute to structural response. This set of
conditions allows the introduction of an effective action, defined as the loading process reconstructed
retaining only those loading modes that excite the structure. This paper discusses this method and the
related concepts by analyzing a set of simple ideal structures in closed form; this approach allows the
formulation of general criteria aimed at defining the effective wind action as a function of non-
dimensional structural and wind parameters. The numerical analysis of a real structure confirms the
tendencies pointed out by the analytical solutions
The annual rate of independent events - A key interpretation for traditional extreme value distributions of wind velocity
No full textThe extreme value theory has been object of engineering studies for more than a century. The analysis of extreme winds plays a key role for complex civil structures and a driving role in different stages of wind turbines lifetime. Most of extremes probability models depend on the annual rate of independent events (ARIE) which has been traditionally considered a constant value. The authors have embraced a recent belief considering the ARIE as a function of the wind velocity. Even though a certain agreement has been achieved across the researches, some issues are still pending. In this regard, the paper shows that the annual, seasonal and daily fluctuations embedded in time series of the mean wind speeds, constrain its probability distribution and time correlation to be physically consistent. Besides, a new physical interpretation of the ARIE is presented, expressing how the independence across wind observations increases with the wind speed, up to the point that all yearly observations are independent if larger than a suitable speed value. Such a tendency is not revealed if the annual, seasonal and daily fluctuations are excluded by the analysis, leading to a deceitful shape of the ARIE. Finally, the paper shows how the velocity-dependent ARIE model is consistent with the conventional asymptotic extreme value theory, if a sufficiently large left-censorship applies to the dataset. The study of the ARIE presented in this paper is based on long-term Monte Carlo simulation of the mean wind speed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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